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Author Topic:   overheating prob.?
steamatic racer
Dirt Full Roller

Total posts: 35
posted June 18, 2002 08:07 AM
Just needing some tips to cure this overheating problem. 355sbc.,restrictor in gooseneck,16" plastic fan,13/1 compression- on racing fuel. I know running lean can cause overheating, so what do you think is a good starting point on jets in a 500cfm.2bbl? I have 82's in it now. THANKS TERP

UFnARacing
Dirt Full Roller

Total posts: 68
posted June 18, 2002 10:46 AM
Not that your question was geared towards this answer, but.....I had a plastic fan on and started to overheat the last couple of weeks. I think the weather was making it run hotter. Switched out the fan to a non-flex aluminum fan from Day Motorsports and now it runs cool. Ran a 25 lap main last weekend with no caution, it never got over 210.

It may be louder and possibly a little horsepower loss, but I'd rather run the cooler temps anyday. Now I can lean the carb out some and not worry about the engine running hot. I had the carb too rich to try and make it run cooler.

Randy

KPLugnut
Dirt Freak

Total posts: 408
posted June 18, 2002 11:57 AM
Another thing you'll want to do is remove that restrictor from the waterneck.
Make sure you are running a well-made shroud around the fan, and duct work aiding in forcing the air that comes in the front of the car to pass thru the radiator.
For more info, read the tech articles on this subject on Stewart waterpumps' website.

Also, unless there is something really "strange" about your 2bbl, that is WAY too much jet....

JMHO,
KPLugnut

[This message has been edited by KPLugnut (edited June 18, 2002).]

racer17j
Dirt Forum Champ
Total posts: 1565
posted June 18, 2002 12:25 PM UIN: 54865418
i agree with uf get a non flex fan those flex fans tend to flatten out and not work very well at hi rpms i had cooling troubles a few weeks ago he's what i found that cured my problemd timing was way wrong shroud had a hole in the top so it wasn't working right i went from 220 durring green and 240 on yellows to 190 on green and 210 on yellows. you might also want to check for a vacume leak as big of jets as you are running

steamatic racer
Dirt Full Roller

Total posts: 35
posted June 18, 2002 12:47 PM
KPLUGNUT, don't I need to restrict the flow of coolant in the radiator to alow it to cool? And when I ran my first hot-laps I had 77's in the carb. & my crew waved me in for the headers were glowing red. Changed to the 82's cured the problem and was told I may want to try 83,84,& 85's. I looked at the plugs the next week after hot-laps (last lap WOT,pushed clutch in & shut off ignition)and they didn't look dark. Thanks for all help though.

steamatic racer
Dirt Full Roller

Total posts: 35
posted June 18, 2002 12:53 PM
RACER17j, on the fan shroud, should it be totally sealed to the rad. and should the fan blades stay back from the shroud alittle?

RangeRover
Dirt Maniac

Total posts: 174
posted June 18, 2002 02:05 PM
We run a similar engine, only less compression (10.5 -1), and with a 4412 2 barrel we run between 82 and 85 jets at sea level. We keep a close eye on the plugs and keep them that textbook tan color. Temps are good, timing is at 35 degrees total advance, and we're fast. I don't believe we have any leaks, so are these jet sizes that uncommon on a 500cfm 2 barrel?

KPLugnut
Dirt Freak

Total posts: 408
posted June 18, 2002 02:39 PM
First things first here. No, you don't need to restrict the water flow. Cooling is not based on time spent in the radiator, since the coolant is then spending MORE time in the hot motor as well. It's all explained very well in Stewarts's article.
Next, on the jetting issues....
A guy at sea level is going to have very different air quality than a guy at 2500ft elevation or more. That's one thing.
Next, nobody is saying what the OTHER differences are in their carbs. Example: what air bleed sizes are being run? What power valves? There's two things that greatly determine final jet size choice for an otherwise identical motor.
Next, cam size will affect it as well. The entire engine combination needs to be considered.

So....in a nutshell, a jet size that seems to work well for one guy, could possibly put another guy way out in left field someplace.

And lastly, about that glowing header thing. That is not necessarily always a lean condition. It is most commonly caused by excessively retarded timing. Stuffing a TON of jet in the carb only masks the real problem, and those two things in combination WILL at times cause an overheating problem in the motor, because you have excess fuel burning well after it is already exiting the motor.

Anyway, I'm starting to ramble here....

KPLugnut

racer17j
Dirt Forum Champ
Total posts: 1565
posted June 19, 2002 01:19 AM UIN: 54865418
i use a stock shroud and it is even with the back side of the fan put a rag in front of the rad and see if it will hold it to it at idle thats a good way to tell if it's sucking enough air mine blew some papers off my dash when i got on it so i can tell it's sucking enough air kp just described to a t what my problem was i had my timing retarded instead of advanced and i was having problems keeping it cool and i was throwing flames out of the pipes

powerglides
Dirt Full Roller

Total posts: 69
posted June 19, 2002 06:10 AM
KP is right I went with the advice on stewartcomponents.com and it solved my problems.

steamatic racer
Dirt Full Roller

Total posts: 35
posted June 19, 2002 07:32 AM
OK, To sum this up, I need to: lose the restrictor(and no thermastat),run the shroud as close to the "steel" or "aluminum" fan as possible and sealed good to the radiator,funnel air to rad.,check timing,,go fast turn left have fun RIGHT?? Anything else? Sure glade to have found this forum. THANKS GUYS JASON TERPENING

steamatic racer
Dirt Full Roller

Total posts: 35
posted June 19, 2002 08:16 AM
KPLUGNUT, That STEWART WATER PUMPS web-site sure did make it clearer.
On the jetting issue, you believe they are abit too much. What info. would you need to cifer out the correct jets? 350 (60)over,13/1 comp.(poppers),461 dubble humps w/ slight clean-up of the exhaust ports,COMP CAMS 12-505-5 284/288-.540/.550 w/ a 106 L.S.,1.5 roller rocker,EDELBROCK VICTOR Jr 2V sportsmans 2bbl. intake,HOLLEY 4412 500cfm 2bbl.& no power valve(used&stock),timing chain 2degrees advance,total timing at 32*,I live in MID-ILL. Anything else? Just ask THANKS TERP

KPLugnut
Dirt Freak

Total posts: 408
posted June 19, 2002 08:21 AM
Right THERE is the reason you are needing to run so much jet in that carb, man. The fact that you are running NO power valve will do it every time. Most carb builders will tell you that blocking off the PV is merely a crutch, and it requires you to compensate with a ton of jet, thereby making the carb nasty rich at idle usually, and STILL running it dangerously lean at times when the power valve circuit would normally be adding extra fuel to the mix.
My recommendation would be drop down to about a 76 jet, and a 4.5 power valve or so, and dial it in from there.
That is....AFTER you iron out the rest of the changes for cooling purposes.

Good luck and let us know how she goes.

KPLugnut

Brad haddix
Dirt Full Roller

Total posts: 56
posted June 19, 2002 09:23 AM
is the # on the power valve the vacuum it takes to keep it closed?

KPLugnut
Dirt Freak

Total posts: 408
posted June 19, 2002 10:09 AM
Yes. But keep in mind, there may be more than one set of #'s you'll find on most Holley power valves. There will usually also be (on the opposing side of the face of the PV) a number and a letter (such as A 2, or something). That corresponds to the month and year of manufacture. So, an "A 2" would mean January 2002.
Hope that helps...

KPLugnut

Brad haddix
Dirt Full Roller

Total posts: 56
posted June 19, 2002 10:45 AM
thanx KP

tilley88
Dirt Freak

Total posts: 353
posted June 20, 2002 01:39 AM
KP is the MAN!!!!!

steamatic racer
Dirt Full Roller

Total posts: 35
posted June 20, 2002 06:53 AM
Well it seems I made a mistake. Last year's carb. was the one w/ no power-valve. This one has the 4.5 in it. So what might be the reason now?
I did all the changes to the cooling system last night; took restrictor out,sealed shroud, & even bought the aluminum 17" fan (non-flex).Ran car 1/2hr. no sign's of over-heating. Should the system pressurize if you only started the engine to move the car maybe 3'?(cold)
THANKS TERP

KPLugnut
Dirt Freak

Total posts: 408
posted June 20, 2002 08:20 AM
It's hard to say why you're getting away with such large jets in a carb with presumably a functioning power valve circuit. I'd have to know how much more work has been done inside the carb in order for it to need jets that big.
Otherwise, tho, it's good to hear you seem to have cooled her down.

Keep us posted and good luck.

KPLugnut

[This message has been edited by KPLugnut (edited June 20, 2002).]

steamatic racer
Dirt Full Roller

Total posts: 35
posted June 20, 2002 10:01 AM
KP, First I want to THANK YOU for taking the time help.
As far as I know the is stock.Like I said before its used & abused. You think maybe if the butterfly shaft is leaking some, that could play a role in it? And as asked in the previest(sp) post should the cooling system be pressurized only after a few seconds of running? Before any of the changes were made to the system, I had moved the car out of the garage. Apon removing the cap, water pressure was present. Just curious, I run this SAT.night and hoping to put more than a side show on. Once again THANKS TERP!!

KPLugnut
Dirt Freak

Total posts: 408
posted June 20, 2002 10:15 AM
I don't think a small vacuum leak at the throttle shaft could cause THAT much of a need to jet up to that extent, but the world of racing carbs never stops amazing me, so anything's possible there. BUT...a more extreme vacuum leak could cause a need for abnormal jetting. It's something you just gotta inspect closely, and leave no detail un-checked.
As for a pressurized system, seems to me, there might be something suspicious there. I don't think THAT much pressure should be present while the system is still relatively cool.....unless of course, you have a head leaking combustion chamber pressure into the system someplace (gasket, crack, etc.).
If there are no other tell-tale signs tho, I would not get TOO worried about it at this point, but don't hold me to that, ok? :-)

And thanks for the "thanks". Just trying to help in any way I can. That's what we do here...help racers everywhere.

KPLugnut

Pickel
Dirt Forum Champ
Total posts: 564
posted June 20, 2002 09:30 PM UIN: 25419780
KPlugnut,
Can you help me out? I have a 355, 11-1 with 64cc heads 202 valve with a victor jr 4 barrel intake with a 500 cfm Holley 2 barrel. My question is I can't run no less than an 84 jet in mine without it running lean. I was overheating also and I went to a cooler plug which brought my temp. down. How do guys run small jets? The only thing that has been done to the motor is the carb. has been honed out for more cfms(somewhere in the 600 series is what I was told) the heads have been matched to the intake gasket. Any ideas would be appreciated.

KPLugnut
Dirt Freak

Total posts: 408
posted June 21, 2002 08:23 AM
There is the reason you need such large jets....you said the carb had been "honed out" to flow more air....more air needs more fuel. Simple answer.
One would hope a knowledgeable pro did the "honing" for you and not just anyone with a die grinder.

Hope that helps....

But if your motor is built that well, with such a large open plenum intake, the motor is going to benefit from more carb than just a stock 4412 anyway.

So...don't get too concerned over the actual jet # your motor requires to run right as compared to other racers.

KPLugnut

Pickel
Dirt Forum Champ
Total posts: 564
posted June 21, 2002 09:17 PM UIN: 25419780
Thanks KPLugnut I understood the part of more air needs more fuel I just thought maybe I was doing something wrong. The carb. was done by a guy who use to build drag motors and he has built some of the carb. for some of guys I race with.

ray14
Dirt Full Roller

Total posts: 67
posted June 21, 2002 11:16 PM
i run a 355 with 4412 holley and my jets are #94s lol wonder why

okokimdachit
Dirt Newbie

Total posts: 1
posted June 24, 2002 07:16 PM
I don't know if anyone else has had this problem,but it happened to us.We bought the 25% reduction pulley for the water pump after wrecking the stock one.Thats when we started having overheating problems.Changed back to 1 to 1 and the problem went away.Local mod.driver told us and in our case this was the problem.

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